HMX – say hello to my little axles

So now that the HMX is on the road, the next big thing I want to accomplish with it is a rear suspension rebuild and axle swap. After scraping away a couple decades’ worth of grease, I discovered the Model 15 axle currently under the car, from a 1982 Spirit GT, is an L-code, which means it’s an open rear with a 2.35:1 gear ratio. Yeah, that’s not a typo. One big reason cars of the early ’80s got such a bad rap was the astronomically high rear-axle ratios, implemented as a band-aid to increase fuel mileage.

While I can dream all day long of bolting in a Twin-Grip Model 20 with mid-3 gears, I’m not holding my breath for one of those. Instead, as always, I’m working with what I got, and what I got is a Model 15 axle out of a ’79 AMX six-cylinder. The K code stamped into the axle indicates a 2.53 gear ratio. (If this axle had come from a California car, it would have had a 3.08 ratio; high-altitude AMXs got a 2.73 ratio. Instead, I got a lowly 49-stater axle.)

So I’ll clean up this K-code axle, along with an AMX-only four-leaf rear suspension. Then after that hope that someday I’ll come across the axle of my dreams.

UPDATE (29.June 2009): Carl Van Deusen called just after he read this post. Carl, btw, is the owner of the 401-powered Gremlin we spotted at Musclepalooza VI. Carl let me know that I shouldn’t worry too much about gear ratios: He was running 14s in the Grem with 2.73 gears.

Dan Rothqsays:

June 29, 2009 9:50 am

Daniel Strohlsays:

June 29, 2009 10:11 am

I believe you’re thinking of the Dana 35, which was the evolution of the AMC Model 20. I have considered it, but I believe they’re just a bit too wide, and swapping one in would require relocating the spring perches.